The invention is an optical glare limiter, as used in vehicles in particular.
It is well known that the ability of the human eye to register and perceive contrast, color and forms of the exterior world more or less quickly depends, besides the adaptability of the eye, essentially on the brightness of the light hitting the eye and the differences in the brightness of the field of vision. If the brightness in the field of vision is too high the eye""s performance may be significantly impaired. Such an impairment of the basic function of the eye is described as blinding.
It is also well-known that in night traffic quite a number of accidents can be attributable to mistakes or false reactions of the driver due to blinding of the human eye. When driving at night the cilia muscles of the eye are more or less relaxed, depending on the focal point of the object being observed. The pupil is relatively wide open and the eye adjusted to the average brightness of the field of vision. If, for instance, the average brightness changes with the light of an oncoming vehicle, the adjustment from one state to another requires a certain period of time, which depends on the previous lighting of the eye, the direction of the adjustment and the difference in brightness before and after adjustment. The larger the difference of the brightness from the oncoming vehicle before the adjustment, the more the retina is irritated, increasing the demands on the speed of the light and dark adjustment and leading to a veil in the retina through the scattered light inside the eye and then to reduced vision. The consequences are, amongst others, that oncoming traffic is only recognized to late or is not sharply focused and distances are improperly estimated and inappropriate reactions by the driver are initiated.
The increasing percentage of xenon-based headlights is increasing the danger of the damaging influences of the increased power of this type of headlight even more compared to the conventional halogen headlight. Investigations have shown that test persons of every age group are disturbed by the xenon headlights in general and independent of the measurable impairment of vision. In particular elderly persons may no longer be able to determine contrasts when looking into xenon lights. (Der Spiegel, 7/1998, pg. 168 ff).
From DE 42 18 436 A1 it is now known that there is a lighting element for vehicles that reduces the blinding effect of oncoming traffic at night. The lighting element is installed in the interior of the vehicle in the area of the driver so that a light source is attached outside the drivers field of vision in a way that a part of the light is directed at the driver""s face, whereby the light source is linked to the headlights of the vehicle in such a manner that the light source shines when the car lights are turned on. With the aid of sensors the light source is turned on when light comes from oncoming traffic.
The apparent technical solution with DE 42 18 436 A1 has the definite technical disadvantage that it is not able to accomplish the task. A portion of the light from the light source of the lighting element is directed at driver""s field of vision and causes a dangerous blinding effect itself.
The invention has therefore set itself the goal of creating an improved glare limiter, which reduces the blinding effect of external light sources, especially with optical means.
The invention solves the task with an optical glare limiter with the properties of the claim 1. The advantages of the design of the glare limiter invention are found in the characteristics secondary claims 2 to 8.
The invented optical glare limiter has the advantage that is effectively reduces the blinding effect of external light sources in a quite simple manner. It is therefore especially well-suited for use in vehicles. The invented glare limiter protects the driver from the dangerous blinding effect of a point of light as described in the state of the art technology and guarantees almost homogenous and widespread contrast conditions free of blinding within the driver""s field of vision.
When used in night driving the brightness differences in the field of vision resulting from oncoming vehicles are significantly reduced and the blinding effect almost completely compensated. The road is clearly seen and the driver is in the position to properly take in the traffic situation.
The blinding effect of oncoming traffic is generally to be found with a distance between the vehicles starting at about 75 m. Below that distance the driver of the effected vehicle is driving almost blind, as a result of the blinding effect. With the optical glare limiter the environment in the area of the driver""s field of vision is illuminated in advance when a vehicle approaches so that the eye adjusts to the higher light intensity in time and the blinding effect of the oncoming vehicle is only slight in the blinding range of 75 m. The early environmental illumination of the driver""s field of vision allows the brightness differences of the light from oncoming, and otherwise, blinding headlights to only have a limited effect on the human eye. Neither blinding nor glare from the windshield can lead to hazardous effects on the eye""s performance. The demands on the adaptability of the human eye are significantly reduced. This is particularly important for elderly drivers due to the fact that the time needed for adaptation to light and dark with changing optical perceptions takes longer. Positive effects are also to be found for nervous drivers.
The reduction of the of the brightness differences in the field of vision also has the advantage that the eye and the driver do not tire as quickly, with the resulting positive emotional effect on the mood and the driver""s performance. A preferred form of execution of the invented glare limiter assures a basic lightness keeping the pupil as a level of brightness as with a homogenous lighting close to that of the waking state during the day, so that the pupil is not subjected to a radical change even with otherwise varying brightness from oncoming vehicles.